fix(fix-owner): chownr.sync quits on non-root uid

- Replicates logic that prevents non-root users from trying to change
file ownership that is present in async version but missing in
`chownr.sync`
- test: Add test coverage to lib/utils/fix-owner.js module

Author: ruyadorno

Diff for: lib/util/fix-owner.js

@@ -77,6 +77,11 @@ function fixOwnerSync (cache, filepath) {
   }
   const { uid, gid } = inferOwner.sync(cache)
   getSelf()
+  if (self.uid !== 0) {
+    // almost certainly can't chown anyway
+    return
+  }
+
   if (self.uid === uid && self.gid === gid) {
     // No need to override if it's already what we used.
     return

Diff for: test/util.fix-owner.js

@@ -0,0 +1,253 @@
+'use strict'
+
+const os = require('os')
+
+const { test } = require('tap')
+const requireInject = require('require-inject')
+const uniqueFilename = require('unique-filename')
+
+// defines reusable errors
+const genericError = new Error('ERR')
+genericError.code = 'ERR'
+const missingFileError = new Error('ENOENT')
+missingFileError.code = 'ENOENT'
+const pathExistsError = new Error('EEXIST')
+pathExistsError.code = 'EEXIST'
+
+// helpers
+const CACHE = require('./util/test-dir')(__filename)
+const filename = uniqueFilename(os.tmpdir())
+const getuid = process.getuid
+const patchesGetuid = (t) => {
+  process.getuid = () => 0
+  t.teardown(() => { process.getuid = getuid })
+}
+const getFixOwner = (opts) => requireInject('../lib/util/fix-owner', opts)
+
+// chownr and chownr.fix error handling tests
+
+test('attempt to chownr existing path', (t) => {
+  patchesGetuid(t)
+  const fixOwner = getFixOwner({
+    chownr: function chownr (path, uid, gid, cb) {
+      cb(missingFileError)
+    },
+    'infer-owner': () => Promise.resolve({})
+  })
+
+  t.plan(1)
+  return fixOwner.chownr(CACHE, filename)
+    .then(res => {
+      t.notOk(res, 'should not throw if path exists')
+    })
+})
+
+test('attempt to chownr unknown error', (t) => {
+  patchesGetuid(t)
+  const fixOwner = getFixOwner({
+    chownr: function chownr (path, uid, gid, cb) {
+      cb(genericError)
+    },
+    'infer-owner': () => Promise.resolve({})
+  })
+
+  t.plan(1)
+  t.rejects(() => fixOwner.chownr(CACHE, filename), 'should throw unknown errors')
+})
+
+test('attempt to chownr using same user', (t) => {
+  patchesGetuid(t)
+  const fixOwner = getFixOwner({
+    'infer-owner': () => Promise.resolve({
+      uid: process.getuid(),
+      gid: process.getgid()
+    })
+  })
+
+  t.plan(1)
+  return fixOwner.chownr(CACHE, filename)
+    .then(res => {
+      t.notOk(res, 'should not throw')
+    })
+})
+
+test('calls setuid setgid to replace user', (t) => {
+  const setuid = process.setuid
+  const setgid = process.setgid
+  process.getuid = () => 0
+  process.setuid = () => undefined
+  process.setgid = () => undefined
+  t.teardown(() => {
+    process.getuid = getuid
+    process.stuid = setuid
+    process.stgid = setgid
+  })
+  const fixOwner = getFixOwner({
+    'infer-owner': () => {
+      process.setuid(process.getuid())
+      process.setgid(process.getgid())
+      return Promise.resolve({
+        uid: process.getuid(),
+        gid: process.getgid()
+      })
+    }
+  })
+
+  t.plan(1)
+  return fixOwner.chownr(CACHE, filename)
+    .then(res => {
+      t.notOk(res, 'should not throw')
+    })
+})
+
+test('attempt to chownr.sync on platforms that do not need ownership fix', (t) => {
+  process.getuid = undefined
+  t.teardown(() => { process.getuid = getuid })
+  const fixOwner = require('../lib/util/fix-owner')
+
+  t.plan(1)
+  return fixOwner.chownr(CACHE, filename)
+    .then(res => {
+      t.notOk(res, 'should not throw')
+    })
+})
+
+test('attempt to chownr.sync existing path', (t) => {
+  patchesGetuid(t)
+  function chownr () {}
+  chownr.sync = () => {
+    throw missingFileError
+  }
+  const fixOwner = getFixOwner({
+    chownr,
+    'infer-owner': { sync: () => ({}) }
+  })
+
+  t.notOk(fixOwner.chownr.sync(CACHE, filename), 'should not throw if path exists')
+  t.end()
+})
+
+test('attempt to chownr.sync unknown error', (t) => {
+  patchesGetuid(t)
+  function chownr () {}
+  chownr.sync = () => {
+    throw genericError
+  }
+  const fixOwner = getFixOwner({
+    chownr,
+    'infer-owner': { sync: () => ({}) }
+  })
+
+  t.throws(() => fixOwner.chownr.sync(CACHE, filename), genericError, 'should throw unknown errors')
+  t.end()
+})
+
+test('attempt to chownr.sync using same user', (t) => {
+  patchesGetuid(t)
+  const fixOwner = getFixOwner({
+    'infer-owner': {
+      sync: () => ({
+        uid: process.getuid(),
+        gid: process.getgid()
+      })
+    }
+  })
+
+  t.notOk(fixOwner.chownr.sync(CACHE, filename), 'should not throw')
+  t.end()
+})
+
+test('attempt to chownr.sync on platforms that do not need ownership fix', (t) => {
+  process.getuid = undefined
+  t.teardown(() => { process.getuid = getuid })
+  const fixOwner = require('../lib/util/fix-owner')
+
+  t.notOk(fixOwner.chownr.sync(CACHE, filename), 'should not throw')
+  t.end()
+})
+
+test('uses infer-owner ids instead of process-retrieved if valid', (t) => {
+  const getgid = process.getgid
+  process.getuid = () => 0
+  process.getgid = () => 1
+  t.teardown(() => {
+    process.getuid = getuid
+    process.getgid = getgid
+  })
+  t.plan(3)
+  function chownr () {}
+  chownr.sync = (path, uid, gid) => {
+    t.equal(path, filename, 'should match filename')
+    t.equal(uid, 501, 'should match uid')
+    t.equal(gid, 20, 'should match gid')
+  }
+  const fixOwner = getFixOwner({
+    chownr,
+    'infer-owner': {
+      sync: () => ({
+        uid: 501,
+        gid: 20
+      })
+    }
+  })
+
+  fixOwner.chownr.sync(CACHE, filename)
+})
+
+// mkdirfix and mkdirfix.sync error handling tests
+
+test('attempt to mkdirfix existing path', (t) => {
+  const fixOwner = getFixOwner({
+    mkdirp: function mkdirp (path, cb) {
+      cb(pathExistsError)
+    }
+  })
+
+  t.plan(1)
+  return fixOwner.mkdirfix(CACHE, filename)
+    .then(res => {
+      t.notOk(res, 'should not throw if path exists')
+    })
+})
+
+test('attempt to mkdirfix unknown error', (t) => {
+  const fixOwner = getFixOwner({
+    mkdirp: function mkdirp (path, cb) {
+      cb(genericError)
+    }
+  })
+
+  t.plan(1)
+  t.rejects(() => fixOwner.mkdirfix(CACHE, filename), 'should throw unknown errors')
+})
+
+test('attempt to mkdirfix.sync existing path', (t) => {
+  function mkdirp () {}
+  mkdirp.sync = () => {
+    throw pathExistsError
+  }
+  const fixOwner = getFixOwner({ mkdirp })
+
+  t.notOk(fixOwner.mkdirfix.sync(CACHE, filename), 'should not throw if path exists')
+  t.end()
+})
+
+test('attempt to mkdirfix.sync unknown error', (t) => {
+  function mkdirp () {}
+  mkdirp.sync = () => {
+    throw genericError
+  }
+  const fixOwner = getFixOwner({ mkdirp })
+
+  t.throws(() => fixOwner.mkdirfix.sync(CACHE, filename), genericError, 'should throw unknown errors')
+  t.end()
+})
+
+test('attempt to mkdirfix.sync but no dir created', (t) => {
+  function mkdirp () {}
+  mkdirp.sync = () => {}
+  const fixOwner = getFixOwner({ mkdirp })
+
+  t.notOk(fixOwner.mkdirfix.sync(CACHE, filename), 'should not throw')
+  t.end()
+})